This foams are very good, they fit perfectly in your ears and the sound does not change a bit!

I've ordered 3 of these replacement packs for a couple of pair of Shure earphones over the last couple of years.

The sound isolation from the foam is excellent, they are fairly easy to use, and fall out less easily than any other option I've tried. Probably only custom-fit molding works much better.

The passive sound isolation is better than active noise cancellation by manufacturers such as Bose, as numerous studies have shown. I'm always amused by the Bose-users on airplanes who don't realize they would get better sound from tiny earphones like Shure or Etymotic than their 5lb monsters with batteries.

Only two minor caveats, one of which should be temporary - (1) There are no Shure earphones with the button for an iPhone yet, only an adaptor, this must be fixed soon. (2) It takes a bit of force and finesse to put the new foams on the earpieces, I haven't had trouble but some might.

[added 1/13/08 - just tried the new black foams, see my review, not quite as secure, same sonics, better looks, more expensive]

I wish they sold them by the case. They stay in pretty well in the gym, and I love the ability to change them when I want, I hate skeevy.

Thanks. These are the best earphone foams for Shure earphones. Perfect fit.

I tried all the rubber vinyl plugs that came with the E3C's, but they all had the shortcoming of not effectively sealing the ear canal making bass very poor, and they were uncomfortable. The yellow foam plugs are easy to use and work just like the ear foams many people use in industrial applications. They effectively seal the ear canal and are very comfortable. Although they seem a bit expensive I've found that once they get dirty you can use water and a bit of dish detergent to clean them. Just soak, squeeze, rinse and let them air dry and they are as good as new. You can do this three or four times, then just toss them away.

Highly recommended.